Hi,
I had the same issue with a 1 year old project already in production.
My UIRequiredDeviceCapabilities is armv7. However, I did not change the UIRequiredDeviceCapabilities as for what I understood the armv7 feature is in line with iPad devices. (unless you do not have any specific requirements)
After below steps my app was approved:
in Xcode:
1) Edit > Convert > To Current Swift Syntax...
2) I changed the Target Device Family (in Project) from iPhone to Universal
hope this can help someone ;-)